Gate controlled electronic switch



Oct. 17, 1967 A. @DARD 3,348,073

GATEYCONTROLLED ELECTRONIC SWITCH Filed June 21, 1965 Invenor mum c mam-a Florney United States Patent 3,348,073 GATE CONTROLLED ELECTRONIC SWITCH Albert Oudard, Grenoble, Isere, France, assignor to Etablissements Merlin & Gerin, Societe Anonyme, Grenoble, Isere, France Filed June 21, 1965, Ser. No. 465,511 Claims priority, application France, June 25, 1964,

79,689 2 Claims. (Cl. 307-885) ABSTRACT OF THE DISCLOSURE This invention relates to electronic switches comprising a bistable semi-conductor switch. 7

There are already known silicon gate controlled semiconductor switches in which both the turning on and oif of the switches is effected by the application of trigger pulses of suitable polarity, duration and amplitude to the control electrode of the switch. These switches are known also under the name of GTO (gate turn 01f) diodes and they are generally composed of a semi-conductor with three terminals and four layers (pnpn). In the known connections, the trigger pulses for these switches are emitted by the secondary winding of a pulse transformer, the primary winding of which is fed from a direct current supply through a resistor and a mechanical interrupter connected in series. This known device has the drawback that the mechanical switch operates under charge so that sparking occurs at the breaker points during their opening movement. The sparks produce wear and erosion of the contacts which must frequently be changed.

On the other hand the opening position of the mechanical switch corresponds to the closing portion (turned on) of the semi-conductor switch and vice versa so that the device cannot be incorporated in an automobile ignition system without considerable modifications of the electrical and mechanical arrangements.

It is an object of the invention to provide a semi-conductor switch of simple construction capable to equip existing automobile ignition systems.

This and other objects will become apparent from the following description of an embodiment of the invention. The annexed drawing shows the diagram of an electronic switch according to the invention.

In this diagram, a charge formed by a resistor R is' connected to a direct current network by means of a gate controlled switch of the type mentioned (GTO diode). The low power trigger pulses for the switch are emitted by the secondary Winding S of a pulse transformer T. The primary winding P of the transformer T is connected by a diode or rectifier D and a resistor R to a source of direct current U preferably having a low internal impedance. A mechanical contact C can short-circuit the branch of the circuit containing the primary winding P and the diode D.

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The switch functions in the following manner:

Assuming that the contact C is closed, a current i limited by the resistor R and by the internal impedance of the source U, flows through the resistor R and the contact C. No current flows through the primary winding P.

On opening of the contact C, a stepped voltage is suddenly applied to the primary winding P of the transformer T by means of the diode D. There is then produced at the terminals of the secondary winding S a voltagehaving a very rigid front (the transformer T being duly dimensioned) and the amplitude of which is substantially equal to that of the voltage applied to the primary winding P multiplied by the ratio of the transformer. The'duration of the trigger pulse is a function of the time constant of the circuit, and the negative polarity (with respect to the cathode of the GTO diode) of the pulse is obtained through the winding direction of the transformer T. This pulse, applied to the control electrode :2 of the GTO diode, causes turning off of the latter and opening of the electronic switch. It should be noted that the opening of the contact C does not produce sparks, in view of the low amplitude of the current i and the ohmic nature of the interrupted circuit.

To close the switch, a positive trigger pulse must be applied to the electrode e and this pulse is produced through the closing of the contact C. The said closing of the contact C causes the current i to flow again through the resistor R and the contact C and the sudden disappearance of the voltage at the terminals of the primary winding P and the diode D produces a current i flowing through the primary winding P, the contact C and the diode D. This current i emanates from the energy stored in the transformer T. There results a voltage of positive polarity (with respect to the cathode of the GTO diode) at the terminals of the Winding S, the amplitude of which voltage depends on the quantity of energy stored in the transformer and on the ratio of the latter but is limited by the voltage appearing at the terminals of the diode D which is acted on in the direct sense.

In consequence the control circuit which has just been described makes it possible to obtain at the electrode 2 firstly a negative pulse having a rigid front and the amplitude of which is substantially equal to that of the source S if the ratio of the transformer T is equal to 1 (the resistance of R and that of the diode D being very low), and secondly a positive pulse having a less steep but adequate front, the amplitude of which is substantially equal to that of the voltage appearing at the terminals of the diode D it the ratio of the transformer is equal to 1. This thus makes it possible, by a judicious choice of elements, to obtain square trigger pulses of suitable amplitude, duration and polarity.

It will be noted that the transformer T makes it possible to separate the auxiliary source S completely from the main network. Moreover it will be realised that the diode D, by limiting the amplitude of the positive pulses, avoids an overloading or destruction of the GTO diode.

It is possible to replace the contact C by a static element performing the same function without going beyond the scope of the invention.

What is claimed is:

1. An electronic switch comprising a pulse transformer having a primary winding and a secondary winding, a first circuit comprising said secondary winding and a gate controlled semi-conductor device operatively connected thereto to be alternately turned on and turned off by application of trigger pulses of opposite polarity applied to the gate of said device by said secondary winding, a sec- 0nd circuit comprising, successively connected'in a closed series loop a supply source of direct current, a resistor, a

a diode, and said primary Winding; and means for selectively short circuiting said diode and said primary winding for producing said trigger pulses.

2. An electronic switch as claimed in claim 1 in which said short circuiting means isa mechanical interrupter.

References Cited' UNITED STATES PATENTS 3,127,522 3/1964 Thorndyke 307-885 ARTHUR GAUSS, Primary Examiner.

J. ZAZWORSKY, Alrsistant Examiner. 

1. AN ELECTRONIC SWITCH COMPRISING A PULSE TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, A FIRST CIRCUIT COMPRISING SAID SECONDARY WINDING AND A GATE CONTROLLED SEMI-CONDUCTOR DEVICE OPERATIVELY CONNECTED THERETO TO BE ALTERNATELY TURNED ON AND TURNED OFF BY APPLICATION OF TRIGGER PULSES OF OPPOSITE POLARITY APPLIED TO THE GATE OF SAID DEVICE BY SAID SECONDARY WINDING, A SEC- 